1. Field of the Invention
The present invention relates to a solid-state image sensor and a camera in which the solid-state image sensor is mounted.
2. Description of the Related Art
A CMOS solid-state image sensor includes a pixel array in which a plurality of pixel units is arranged two-dimensionally. The pixel array includes a plurality of column signal lines. In the CMOS solid-state image sensor, each pixel unit includes at least one photoelectric converter, and an amplifier transistor which outputs, to a column signal line, a signal corresponding to charges accumulated in the photoelectric converter. When the pixel unit includes a plurality of photoelectric converters, the photoelectric converters can share one amplifier transistor. The CMOS solid-state image sensor further includes a current source which defines the magnitude of a current flowing through the column signal line. The current source and the amplifier transistor of the pixel unit form a source follower circuit. The source follower circuit outputs a signal from the pixel to the column signal line.
In the solid-state image sensor, as the number of pixels increases, the number of column signal lines in the pixel array and the number of current sources connected to them also increase. This increases power consumption.